<div class="refentry" lang="en" xml:lang="en"><a id="glShadeModel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glShadeModel — select flat or smooth shading</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glShadeModel</b>(</code></td><td>GLenum  </td><td><var class="pdparam">mode</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p>
                    Specifies a symbolic value representing a shading technique.
                    Accepted values are <code class="constant">GL_FLAT</code> and <code class="constant">GL_SMOOTH</code>.
                    The initial value is <code class="constant">GL_SMOOTH</code>.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            GL primitives can have either flat or smooth shading.
            Smooth shading,
            the default,
            causes the computed colors of vertices to be interpolated as the
            primitive is rasterized,
            typically assigning different colors to each resulting pixel fragment.
            Flat shading selects the computed color of just one vertex
            and assigns it to all the pixel fragments
            generated by rasterizing a single primitive.
            In either case, the computed color of a vertex is the result of
            lighting if lighting is enabled,
            or it is the current color at the time the vertex was specified if
            lighting is disabled.
        </p><p>
            Flat and smooth shading are indistinguishable for points.
            Starting when <a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> is issued and counting vertices and
            primitives from 1, the GL gives each flat-shaded line segment
            <math overflow="scroll"><mi mathvariant="italic">i</mi></math>
            the
            computed color of vertex
            <math overflow="scroll">

                <mrow>
                    <mi mathvariant="italic">i</mi>
                    <mo>+</mo>
                    <mn>1</mn>
                </mrow>
            </math>,
            its second vertex.
            Counting similarly from 1,
            the GL gives each flat-shaded polygon the computed color of the vertex listed
            in the following table.
            This is the last vertex to specify the polygon in all cases except single
            polygons,
            where the first vertex specifies the flat-shaded color.
        </p><p>
        </p><div class="informaltable"><table><colgroup><col /><col /></colgroup><thead><tr><th><span class="bold"><strong>
                        Primitive Type of Polygon
                        <math overflow="scroll"><mi mathvariant="italic">i</mi></math>
                        </strong></span></th><th class="center"><span class="bold"><strong>
                        Vertex
                        </strong></span></th></tr></thead><tbody><tr><td>
                        Single polygon
                        (<math overflow="scroll">

                            <mrow>
                                <mi mathvariant="italic">i</mi>
                                <mo>==</mo>
                                <mn>1</mn>
                            </mrow>
                        </math>)
                        </td><td class="center">
                        1
                        </td></tr><tr><td>
                        Triangle strip
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mi mathvariant="italic">i</mi>
                                <mo>+</mo>
                                <mn>2</mn>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Triangle fan
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mi mathvariant="italic">i</mi>
                                <mo>+</mo>
                                <mn>2</mn>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Independent triangle
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mn>3</mn>
                                <mo>⁢</mo>
                                <mi mathvariant="italic">i</mi>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Quad strip
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mn>2</mn>
                                <mo>⁢</mo>
                                <mi mathvariant="italic">i</mi>
                                <mo>+</mo>
                                <mn>2</mn>
                            </mrow>
                        </math>
                        </td></tr><tr><td>
                        Independent quad
                        </td><td class="center">
                        <math overflow="scroll">

                            <mrow>
                                <mn>4</mn>
                                <mo>⁢</mo>
                                <mi mathvariant="italic">i</mi>
                            </mrow>
                        </math>
                        </td></tr></tbody></table></div><p>
            Flat and smooth shading are specified by <code class="function">glShadeModel</code> with <em class="parameter"><code>mode</code></em> set to
            <code class="constant">GL_FLAT</code> and <code class="constant">GL_SMOOTH</code>, respectively.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is any value other than
            <code class="constant">GL_FLAT</code> or <code class="constant">GL_SMOOTH</code>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glShadeModel</code>
            is executed between the execution of <a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
            and the corresponding execution of <a class="citerefentry" href="glEnd"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SHADE_MODEL</code>
        </p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>,
            <a class="citerefentry" href="glColor"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a>,
            <a class="citerefentry" href="glLight"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,
            <a class="citerefentry" href="glLightModel"><span class="citerefentry"><span class="refentrytitle">glLightModel</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></div>
